Morrowind.
Wait no, with Bloodmoon that could actually be great fun. "WAIT COME BACK! I JUST WANT TO NIBBLE AT YOUR LEG! OH COME ON, JUST A FINGER? COME ON! YOU OWE ME FOR THAT SWORD I GAVE YOU! COME ON! I NEED TO EAT!"
Hmm... I'd say Black and White 2. I think it would just sort of remove the fun of being an all-powerful God, for many reasons. A Competitive Mode maybe, Co-Op, no.